Devices for blow moulding containers have long been known from the prior art. In this case plastic parisons, which are usually heated, are acted on by compressed air in order in this way to be reshaped into plastic containers. Such devices for reshaping plastic parisons into plastic containers usually have a blow wheel on which a plurality of blow stations is disposed. These blow stations in turn form hollow spaces within which the plastic parisons are expanded.
The compressed air is usually supplied to the plastic parisons by means of blow moulding dies. The blow pressure necessary for expansion of the plastic parisons is usually provided by means of valve blocks. Various configurations of these valve blocks or valve mechanisms are known from the prior art.
EP 1 328 396 B1 describes a blow moulding machine with a control valve mounted on the blow moulding device for controlling the blow air. In this case a valve body is provided which surrounds the blow moulding die in an annular manner at least over a part of its height. A low-pressure valve, a high-pressure valve and a venting valve are distributed over the periphery of the valve support and are connected to the blow moulding die by bores in the valve support.
A device for blow moulding containers is known from EP 1 271 029 B1. This device has a unit for pneumatically controlling the blow pressure and this unit has a control piston which is guided in a cylinder and is mounted in the direction of a longitudinal axis. In this case this control piston is constructed at least in some regions from a plastic. Due to this construction of some regions of the control piston from plastic a metal contact with the wall of the cylinder is avoided. In this way separate guide strips can be avoided. In addition this control piston made from plastic also has a lower weight and a reduced mass moment of inertia.
Although this device operates satisfactorily, it has been shown that some of the control pistons produced in this way are subject to increased wear.
Therefore it may be desirable to provide a device for blow moulding containers which has a longer service life.